1. Field of the Invention
The present invention relates generally to a linear motion guide unit adapted for use in various types of machinery such as semiconductor manufacturing machines, precision measuring instruments, inspection equipment, precision assembly machines and, more particularly, to a linear motion guide unit in which a slider is movable on an elongated track rail by virtue of rollers that are allowed to run through recirculating circuits, together with separators each interposed between any two adjacent rollers.
2. Description of the Prior Art
Although current linear motion guide units have been used extensively in diverse fields of machinery such as semiconductor manufacturing machines, measuring/inspection instruments, and so on, the scope of their useful applications is still expanding with the development of technology. To this end, the linear motion guide units are seeing growing demands for less noise or vibration, reduction of wear, long-lasting service life, high precision, high-speed sliding motion, easy assembly, versatile usage, and so on. In recent years, especially, the linear motion guide unit is much expected in which separators are each interposed between any two adjoining rolling elements to lower noise, reducing wear thereby realizing long-lasting service life.
Disclosed in Japanese Patent Laid-Open No. 132745/2001 is a linear motion rolling guide unit in which flanged separators are each interposed between any two adjoining rollers, with their flanges coming into engagement with axially opposite ends of the rollers to keep the separators against axial deviation or offset thereby to make certain of smooth sliding movement with no noise of the separators. With the prior linear motion rolling guide unit recited earlier, the separators are each composed of a major body made concaved at opposite sides thereof to accommodate therein the adjacent rollers in a rolling contact relation, one to each side, and flanges arranged at the axial opposite ends of the major body, one to each end, in a way extending in opposite directions to each other along the moving direction of the rollers to come into face-to-face engagement with their associated axial ends of the adjacent rollers. The separator constructed as stated just above may be well kept against any offset in axial direction of the roller with no need of specific guide member, because the roller rolls in a condition that they are regulated at their axial opposite ends to run through a recirculating circuit. In the prior linear motion rolling guide unit in which the separators have flanges on their axial ends, there is a major drawback that the recirculating circuit has to be made large in width by thickness of the flanges on the separators, compared with the linear motion guide unit of the sort having no separator. Moreover, the separator recited earlier is disadvantageously made too smaller in outside periphery diameter than the roller to embrace the associated rollers therein.
In Japanese Patent Laid-Open No. 26017/1989 there is disclosed a rolling means to guide parts in linear direction, in which many rollers are held by means of spacers that come in engagement at their sidewise ends thereof with recesses formed in skids. The spacers are each made sidewise extended beyond opposite axial ends of the roller to form sidewise opposed lugs, which come in engagement with the recesses formed inside recirculating grooves in the skids, thereby holding the rollers in place. With the rolling means constructed as recited earlier, the troublesome work must be done to provide sidewise lugs for the spacers. Moreover, the recesses in which the lugs of the spacers fit in a sliding engagement have to be cut into the overall inside of the recirculating grooves. The lugs of the spacers are sensitive to be subject to damage such as wear that might be caused by the continuous sliding engagement with the inside surfaces of the recesses.
Another prior linear motion system disclosed in Japanese Patent Laid-Open No. 314420/2000 has spacers for linear motion, which are each interposed between any two adjoining rollers. The spacer is made hollow to experience elastic deformation in moving direction of the rollers and also is provided at the center thereof with a guide plate extending radially outwardly into a guide channel that is cut in the moving direction in an inside periphery of a recirculating circuit where the rollers run through there. In this prior linear motion guide unit, however, the spacer has to be designed lest it comes in interference at any edge thereof with the inside surface of the roller-recirculating circuit. The troublesome work is further needed to cut the guide channel, in which the guide plate fits for free movement, in the overall inside surface of the roller-recirculating circuit. Moreover, the guide plate is apt to be subject to damage such as wear, since the guide plate comes most often in sliding engagement with the walls in the associated guide channel, but not always.
Nevertheless, the current linear motion guide units, as coming used in the machines that are getting faster in operating speed and cycle, must be further refined on quietness, high accuracy and wear proof in operation. With the prior linear motion guide unit having any separator interposed between two adjoining rollers, moreover, any construction that the separator travels with keeping to fit snugly over the rollers flanking the forward and aft ends of the separator is critical for making sure of steady movement of the rolling elements throughout the roller-recirculating circuit even under modern high-speed operation. For allowing the separator in the linear motion guide unit to move with fitting over the associated rollers, it will be sufficient only to get the separator concaved on the forward and aft sides thereof flanking the adjacent rollers and made large in outside diameter to what extent the separator may fit over the overall roller.
As the separator travels in a sliding manner as opposed to the roller that moves in rolling manner, however, the separators made large in outside diameter would pose a major problem that they, when traveling through a turnaround in the recirculating circuit, might tend to experience an interference with an inside surface of the turnaround, incurring travel failure. Thus, it remains a major challenge to provide the separator that, even though made large in outside diameter enough to fit over the overall roller, is allowed to recirculate steady, smoothly together with the rollers flanking the forward and aft sides of the separator through, especially, the turnaround in the roller-recirculating circuit.
Recently many types of linear motion guide units have been developed in which separators are each interposed between any two adjoining rollers to lessen noise and wear, and increase life span of the associated parts. Especially the present inventor has already developed a linear motion guide unit in which more than one separator made large in outside diameter thereof is interposed between any two adjoining rolling elements of balls. This linear motion guide unit was filed in Japan in the name of the present applicant under Patent Application No. 2001-391276. With the linear motion guide unit that the separator made large in outside diameter are interposed between any two adjoining balls as recited just above, the turnaround is made on a radially inside curved surface thereof with a gutter for relief to make certain that the separator is allowed to travel through the turnaround without seeing any interference with the inside surface of the turnaround. Application of the technical conception developed earlier to a linear motion guide unit using rollers rather than balls for the rolling elements has resulted in the development of the present invention about how to define the relation of the separator with the turnaround in the roller-recirculating circuit.
The present invention, therefore, has as its primary object to overcome the major problem discussed earlier and in particular to provide a linear motion guide unit in which a separator interposed between any two adjoining rollers fits over or embraces substantially the overall semicylindrical surface of each roller to be allowed to run together with the rollers steady, smoothly through a roller-recirculating circuit, especially through a turnaround without causing rattling sound between the separator and the rollers flanking the separator, thereby making sure of realizing the reduction of noise and wear, and the high accuracy of operation. To make certain that the separator, even though made large in outside diameter thereof, is allowed to travel smoothly through the turnaround in the recirculating circuit, especially according to the present invention, a linear motion guide unit is provided in which the turnaround is made on a radially inside curved surface thereof with a gutter for relief, while the separator is made with a sunken relief whereby the separator is helped to move smoothly together with the roller through the turnaround in the recirculating circuit.
The present invention is concerned with a linear motion guide unit comprising; a track rail having a lengthwise side on which a first raceway extends lengthwise thereof, a slider having a second raceway confronting the first raceway and lying for sliding movement relatively to the track rail by virtue of more than one roller that are allowed to roll through a load racecourse defined between the first and second raceways, a separator interposed between any two adjoining rollers so as to be allowed to recirculate together with the rollers through a recirculating circuit that is composed of the load racecourse, turnarounds made in the slider to be connected with the load racecourse, and a return passage made in the slider to be connected with the turnarounds; wherein the separator is made concaved on forward and aft sides flanked by the adjacent rollers to provide concave surfaces that fit over the rollers in rolling-contact relation, the concave surface having a length and a width that are able to fit over substantially overall semicircular surface of the roller.
In one aspect of the present invention, a linear motion guide unit is provided in which the separator has the width making up substantially about 96% of a diameter of the roller and the length reaching substantially about 98% of an axial length of the roller.
In another aspect of the present invention, a linear motion guide unit is provided in which the separator is made with a sunken relief on at least an inward side thereof, which is near a radially inside curved surface in the turnaround, the sunken relief extending lengthwise of the separator and being provided by making the separator reduced in width lest the separator comes in engagement with the radially inside curved surface in the turnaround.
In another aspect of the present invention, there is provided a linear motion guide unit wherein a gutter for relief is cut in the radially inside curved surface in the turnaround in a way extending circumferentially along the turnaround, thereby keeping the separator from coming in any interference with the radially inside curved surface in the turnaround when the separator travels through the turnaround.
In another aspect of the present invention, there is provided a linear motion guide unit wherein the sunken relief made on the separator to keep the separator from coming in any interference with the radially inside curved surface in the turnaround lies midway between lengthwise ends of the separator, while gutters for relief cut in the radially inside curved surface in the turnaround are placed at sidewise opposite sides of the radially inside curved surface in the turnaround, one to each side, to keep the radially inside curved surface in the turnaround from coming in any interference with the separator at raised portions that are left on lengthwise opposite ends across the sunken relief of the separator.
In a further another aspect of the present invention, there is provided a linear motion guide unit in which sunken relieves made on the separator to keep the separator from coming in any interference with the radially inside curved surface in the turnaround lie on the lengthwise ends of the separator, one to each end, while the gutter for relief cut in the radially inside curved surface in the turnaround is placed midway between the opposite sides of the radially inside curved surface in the turnaround to keep the radially inside curved surface in the turnaround from coming in any interference with the separator at a raised portions that are left midway between the lengthwise opposite sunken relieves of the separator.
In another aspect of the present invention, a linear motion guide unit is provided in which the separator is made in symmetry on sidewise opposite sides of an axis. With the linear motion guide unit constructed as stated just above, the separator may be made simple in construction, much easy in production, and also may be assembled easily between the adjacent rollers with no need for considering the direction of what it should.
In another aspect of the present invention, a linear motion guide unit is provided in which the slider is comprised of a carriage including therein the second raceway and the return passage, end caps mounted on forward and aft ends of the carriage, one to each end, and each made therein with turnarounds where the separators together with the rollers are allowed to turn round in rolling direction, end seals attached on end surfaces of the end caps, one to each cap, and a retainer plate fastened to the carriage to extend lengthwise along the carriage to support thereon the rollers.
In another aspect of the present invention, a linear motion guide unit is provided in which the end caps are each made up of an end cap body and a spacer, which are attached to any one of the forward and aft ends of the carriage, the spacer being to provide the radially inside curved surface of the turnaround, which is partially sunken in to form the gutter for relief, and an end cap body being to provide a radially outside curved surface of the turnaround.
In another aspect of the present invention, there is provided a linear motion guide unit in which the spacer, especially, includes a straight area to be conjoined with at least the second raceway on the carriage in flush with one another, and a curved area merging with the straight area. Moreover, the curved area in the spacer is formed in either the overall circular shape or another shape that is made up of sidewise opposite arcs and a linear area lying midway between the arcs.
In another aspect of the present invention, a linear motion guide unit is provided in which the gutter for relief formed on the spacer starts with a slope made in the straight area and extends circumferentially along the curved area of the spacer. According to the aspect of the present invention as stated just earlier, smooth rolling of the rollers through the recirculating circuit would be realized by simply forming the slope on the straight area in the resin-made spacer of the end cap, rather than chamfering the metal-made carriage at the forward and ends to be opened to the associated turnaround.
In a further another aspect of the present invention, a linear motion guide unit is provided in which the track rail is made on a lengthwise side thereof with a first groove to hold therein the retainer plate, the groove being flanked with the first raceways, while the carriage is also made with a second groove to hold the retainer plate, the second groove being flanked with the second raceways lying confronting the first raceways on the track rail.
In another aspect of the present invention there is provided a linear motion guide unit in which the slider fits over astride the track rail for linear motion relatively to the track rail.
With the linear motion guide unit constructed as stated earlier, the separator interposed between any two adjoining rollers is made large in size enough to fit over or embrace substantially the overall cylindrical surfaces of the rollers flanking the separator. Moreover, the gutter for relief is provided on the spacer that defines the radially inside curved surface of the turnaround in the end cap while the sunken relief is provided on the separator lest the large separator comes in any interference with the radially inside curved surface in the turnaround when the separator travels through the turnaround. Thus, the linear motion guide unit of the present invention, even though used at any posture of the vertical, upside down or tilted posture, and so on rather than the horizontal, makes certain of smooth rolling of the rollers through the circulating circuit without causing any chatter or rattling whenever the rollers travel together with the separators. Complementary relation of the gutter for relief extending circumferentially of the radially inside curved surface in the turnaround to the sunken gutter on the separator, moreover, keeps the separator from coming in any interference with the radially inside curved surface in the turnaround. This construction can realize less noise or vibration, reduction of wear, high precision and long-lasting service life, and so on, with even high-speed, high-cycle operation of the rollers in the recirculating circuit.